java.net
Class NegativeCache<K,V>

java.lang.Object
  java.util.AbstractMap<K,V>
      java.util.HashMap<K,V>
          java.util.LinkedHashMap<K,V>
              java.net.NegativeCache<K,V>

All Implemented Interfaces:

Serializable, Cloneable, Map<K,V>

 class NegativeCache<K,V>
extends LinkedHashMap<K,V>

This class is used to manage the negative name lookup cache.

Field Summary

(package private) static float	LOADING
(package private) static int	MAX_NEGATIVE_ENTRIES
(package private) static NegativeCache<String,NegCacheElement>	negCache

Constructor Summary

NegativeCache(int initialCapacity, float loadFactor, boolean accessOrder)
Returns the hostname for the cache element

Method Summary

(package private) static void	checkCacheExists() This method checks if we have created the cache and if not creates it
(package private) static String	getFailedMessage(String hostName) Returns the message that occurred when we failed to lookup the host if such a failure is within the cache and the entry has not yet expired
(package private) static void	put(String hostName, String failedMessage) Adds the host name and the corresponding name lookup fail message to the cache
protected boolean	removeEldestEntry(Map.Entry<K,V> eldest) Returns if we should remove the Eldest entry.

Methods inherited from class java.util.LinkedHashMap

clear, entrySet, get, keySet, put, remove, values

Methods inherited from class java.util.HashMap

clone, containsKey, containsValue, isEmpty, putAll, size

Methods inherited from class java.util.AbstractMap

equals, hashCode, toString

Methods inherited from class java.lang.Object

finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface java.util.Map

equals, hashCode

Field Detail

negCache

static NegativeCache<String,NegCacheElement> negCache

MAX_NEGATIVE_ENTRIES

static final int MAX_NEGATIVE_ENTRIES

See Also:

Constant Field Values

LOADING

static final float LOADING

See Also:

Constant Field Values

Constructor Detail

NegativeCache

NegativeCache(int initialCapacity,
              float loadFactor,
              boolean accessOrder)

Returns the hostname for the cache element

Method Detail

removeEldestEntry

protected boolean removeEldestEntry(Map.Entry<K,V> eldest)

Returns if we should remove the Eldest entry. We remove the eldest entry if the size has grown beyond the maximum size allowed for the cache. We create the LinkedHashMap such that this deletes the least recently used entry

Overrides:

removeEldestEntry in class LinkedHashMap<K,V>

Parameters:

eldest - the map entry which will be deleted if we return true

Returns:

true if the eldest member should be removed

put

static void put(String hostName,
                String failedMessage)

Adds the host name and the corresponding name lookup fail message to the cache

Parameters:

hostName - the name of the host for which the lookup failed

failedMessage - the message returned when we failed the lookup

getFailedMessage

static String getFailedMessage(String hostName)

Returns the message that occurred when we failed to lookup the host if such a failure is within the cache and the entry has not yet expired

Parameters:

hostName - the name of the host for which we are looking for an entry

Returns:

the message which was returned when the host failed to be looked up if there is still a valid entry within the cache

checkCacheExists

static void checkCacheExists()

This method checks if we have created the cache and if not creates it